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DISABILITY |
a Institute on Aging, University of South Florida, Tampa
b Department of Gerontology, University of South Florida, Tampa
Correspondence: Yuri Jang, PhD, Gerontology Center, University of Georgia, 255 East Hancock Avenue, Athens, GA 30602. E-mail: yjang{at}geron.uga.edu.
Decision Editor: Laurence G. Branch, PhD
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Abstract |
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Key Words: Disability • Depression • Mastery • Social resources
Disability has been widely appreciated as one of the important risk factors for late-life depression (Kennedy, Kelman, and Thomas 1990
; Prince, Harwood, Thomas, and Mann 1998; Williamson and Schulz 1992; Zeiss, Lewinsohn, Rohde, and Seeley 1996; for a comprehensive review on late-life disability and depression, refer to Bruce 2001). However, the association between disability and depression is not inevitable. Some individuals with severe disability enjoy a high quality of life, and others may become depressed with minor physical inconvenience. Identification of the factors responsible for these individual variations in outcome is essential to understand the impacts of disability and its consequences.
In the prevailing model of disablement process, Verbrugge and Jette 1994 have suggested that individuals' internal and external resources influence the progression to disability. Recent studies have demonstrated substantial roles of psychosocial factors in the developmental process of disability (Femia, Zarit, and Johansson 1997, Femia, Zarit, and Johansson 2001; Jang, Haley, Mortimer, and Small 2001; Kempen et al. 1999). However, few studies have considered the potential of psychosocial factors to alter the association between disability and depression in contrast to a sizable research that has emphasized physical exercise or rehabilitation to promote functioning and well-being.
Psychological resources and social support have been widely viewed as important coping resources. In particular, social support has been extensively researched, and many longitudinal studies have evidenced that social support protects older individuals against harmful stresses and promotes physical and emotional well-being (Mendes de Leon, Gold, Glass, Kaplan, and George 2001; Oxman, Berkman, Kasl, Freeman, and Barrett 1992; Unger, McAvay, Bruce, Berkman, and Seeman 1999). Because psychological factors reflect individuals' subjective perception and evaluation of situations, they may have substantial roles in adaptation to disability. However, little has been done to explore the potential roles of psychological attributes in the disability–depression relationship, and this relationship is of great interest in the present study.
As a positive emotional state, mastery or sense of control may play an important role in perceiving functioning and well-being. Mastery is defined as the extent to which a person feels that he or she has control over his or her life and environment (Pearlin and Schooler 1978). Numerous studies have shown positive associations of mastery with physical and emotional well-being (Bienenfeld, Koenig, Larson, and Sherrill 1997; Pearlin, Lieberman, Menaghan, and Mullan 1981; Roberts, Dunkle, and Haug 1994; Schieman and Turner 1998; Thoits 1987). Mastery has also been found to provide psychological resilience and to facilitate adaptation under stressful life situations, including medical events (Kempen, Jelicic, and Ormel 1997), functional decline (Femia et al. 1997; Kempen et al. 1999; Reich and Zautra 1991), caregiving (Bookwala and Schulz 1998), and elder mistreatment (Comijs, Pennix, Knipscheer, and van Tilburg 1999).
There is general consensus regarding the positive roles of social resources in responding to life stress and enhancing well-being. Studies have consistently shown that individuals with strong social ties and social interactions are in better physical and mental health (Cohen and Wills 1985; George 1996; Mendes de Leon et al. 2001). In particular, individuals with more social resources have been shown to have a more rapid functional and emotional recovery in health-related stressful situations, such as medical events or injury (Kempen, Scaf-Klomp, Ranchor, Sanderman, and Ormel 2001; Magaziner, Simonsick, Kashner, Hebel, and Kenzora 1990; Wilcox, Kasl, and Berkman 1994) and functional decline (Newsom and Schulz 1996; Wallsten, Tweed, Blazer, and George 1999).
Psychosocial factors may not only directly influence emotional states but may also interact with disability. As suggested by the stress-buffering hypothesis (Cohen and Wills 1985), social support has been shown to modify adverse physical and mental consequences associated with stress (Hays, Steffens, Flint, Bosworth, and George 2001; Penninx et al. 1997; Wallsten et al. 1999). Studies have also shown that individuals' psychological resources attenuate the adversity of stressful life situations and improve adaptation. Mendes de Leon, Seeman, Baker, Richardson, and Tinetti 1996 reported a significant interaction between self-efficacy and changes in physical performance, suggesting that self-efficacy buffers functional decline in the face of diminished physical capacity. Another study (Roberts et al. 1994) showed that greater sense of control significantly altered the negative impacts of stress, defined as daily strains and life events, and protected emotional well-being. Exploring moderating effects of psychosocial resources on depression can identify risk-enhancing and risk-reducing factors, which are relevant to the development of interventions.
Given the potential of psychosocial resources to alter the effects of disability on depression, the following research questions were generated:
We hypothesized that higher levels of mastery and more social resources would attenuate the negative impacts of disability on depression. These research questions were addressed in cognitively intact older individuals because cognitive impairment can affect disability and depression and reduce the validity of self-reported responses.
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Methods |
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). To be eligible to participate, participants had to live in randomly selected blocks of two U.S. Census tracts in Charlotte County and be between the ages of 60 and 84. Individuals living in long-term care facilities were excluded. Invitations to participate in this study were made by sending potential participants a letter indicating that a staff member would be contacting them by telephone within 3–4 days. Up to nine telephone calls were made to age-eligible participants before they were classified as unreachable. Among the 808 persons with whom contact could be established, 466 (57.7%) agreed to participate in the face-to-face interviews. For the present analysis, participants who were cognitively impaired were excluded. This was done by excluding those who scored below 77 on the Modified Mini-Mental State Examination (Teng and Chui 1987), resulting in a sample size of 444. A listwise deletion further reduced the final sample size to 406 participants who had complete records on all of the study variables.
Measures
Disability.
Disability was measured with 17 items from a composite measure consisting of the activities of daily living (Katz 1983), the instrumental activities of daily living (Lawton and Brody 1969), the Physical Performance Scale (Nagi 1976), and the Functional Health Scale (Rosow and Breslau 1966). Individuals were asked to report their functional status for each activity in the list. Responses were coded as 0 (no difficulty), 1 (some difficulty), 2 (a lot of difficulty), or 3 (unable to do). Total scores were calculated by summing responses for the 17 questions. The potential range of scores was 0 (no disability) to 51 (severe disability). Cronbach's alpha for this measure in the present sample was high (
= .82).
Mastery.
Mastery was measured with Pearlin and Schooler 1978 Mastery Scale. Respondents described their feelings about seven items such as "I cannot solve my problems" and "My future mostly depends on me" on a 4-point Likert scale ranging from 1 (strongly disagree) to 4 (strongly agree). Responses to negatively worded items were reverse-coded, and all responses were summed for the total score. Scores on the Mastery Scale ranged from 7 (low mastery) to 28 (high mastery). Cronbach's alpha for this scale was satisfactory in the present sample ( = .78).
Social Resources.
Social resources included three subscales: Social Network, Social Support, and Satisfaction With Support. Social network was measured with six items from Lubben 1988 Social Network Scale. Measures included the number of relatives or friends seen at least once a month (0 to 9 or more), frequency of contact (less than monthly to daily), and the number of relatives or friends the participant felt close to (0 to 9 or more). Cronbach's alpha for social network was high in the present sample ( = .71). Social support and satisfaction with support were measured with a composite measure from the work of Krause and Borawski-Clark 1995. The items in the scale represented various dimensions of social support, including instrumental support (such as help with chores), informational support (such as sharing suggestions and information), and emotional support (such as having others listen and show interest). For each support activity, respondents reported how often they received the support (never to very often). In addition, respondents were asked to report how satisfied they were with the instrumental, informational, and emotional support they received, using a 4-point Likert scale ranging from 1 (not at all) to 4 (very). Cronbach's alpha was found to be satisfactory for Social Support (11 items, = .87) and Satisfaction with Support (3 items, = .68).
Depression.
The Geriatric Depression Scale–Short Form (GDS-SF; Sheikh and Yesavage 1986) was used to assess depressive symptoms. The GDS-SF was designed specifically for the assessment of depressive symptoms in older populations. Respondents describe their feelings about 15 items such as "Do you feel your life is empty?" and "Are you in good spirits mostly?" using a yes/no format. The GDS-SF scores are calculated by counting the number of responses that suggest possible depression. Scores on the GDS-SF ranged from 0 (no depressive symptoms) to 15 (severe depressive symptoms). Cronbach's alpha for this measure was shown to be satisfactory in the present sample ( = .77).
Other Variables.
Demographic information included age (in years), gender (0 = male, 1 = female), marital status (0 = not married, 1 = married), and educational attainment (in years). Chronic conditions were measured with a checklist by asking the respondents whether a doctor had ever told them that they had specific diseases or conditions. The list included 11 chronic diseases and conditions, including heart disease, high blood pressure, diabetes, stroke, cancer, and arthritis. The total number from the list was used in the analysis.
Analytic Strategy
To test direct and moderating effects of psychosocial attributes, a hierarchical regression model of depression was estimated by entering independent blocks of predictors, with the entry order being (a) demographic variables and chronic conditions, (b) disability, (c) mastery and social resources, and (d) interaction terms between disability and psychosocial factors. In computing interaction terms, centered scores were used to avoid problems associated with lack of scale invariance and to minimize the multicollinearity between the direct effects and interaction terms (Aiken and West 1991). The scale transformation was conducted by subtracting the mean from each score. When significant interactions were found, the sample was divided into low and high groups based on the median scores of the moderating factors, and the correlation coefficients between disability and depression in two groups were compared using Fisher's r-to-z transformation, a statistical method to determine the difference between independent correlation coefficients (Steiger 1980).
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Results |
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The mean score for mastery was 21.8 (SD = 3.28; range = 11–28). Social network, social support, and satisfaction with support averaged 19.2 (SD = 4.89; range = 2–30), 24.9 (SD = 7.97; range = 11–44), and 10.4 (SD = 1.88; range = 3–12), respectively. The means for disability and depression were 2.33 (SD = 4.35; range = 0–30) and 1.78 (SD = 2.16; range = 0–14), respectively.
Associations Among Study Variables
To assess underlying associations among study variables, bivariate correlations were examined, and the results are presented in Table 1 . All correlation coefficients were below .50. To reduce confounding resulting from shared variance between physical and mental health, we used GDS-SF (Sheikh and Yesavage 1986) as an index of depression. This scale was designed with items for somatic symptoms excluded, which reduces confounding between physical conditions and mental health. However, a high correlation of disability with depression (r = .45, p < .001) was still obtained. Depression also was highly associated with mastery (r = -.47, p < .001). The strong association between mastery and depression is not surprising because lack of mastery indicates helpless or fatalism. However, numerous studies have shown that mastery and depression are correlated yet distinguished constructs (Bienenfeld et al. 1997; Pearlin et al. 1981; Roberts et al. 1994; Thoits 1987). Given the high associations, results need to be carefully interpreted, and possible confounding among the variables should be kept in mind.
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Predictors of Depression
Table 2 summarizes the results of the hierarchical regression model of depression. Demographic variables and chronic conditions explained 7% of the variance of depression, with lower levels of education and more chronic conditions being significant predictors. Disability explained an additional 15% of the variance. After controlling for background variables and disability, psychosocial resources explained an additional 16% of the variance. Individuals with lower levels of mastery, smaller social network, and less satisfaction with support were more likely to be depressed. In addition to the direct effects, significant interactions were obtained for Disability x Mastery and Disability x Satisfaction With Support. The interaction terms added 3% to the variance explained, resulting in a total of 41% of variance of depression accounted for by the model.
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Discussion |
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In the regression model for direct effects, education, chronic conditions, disability, mastery, social network, and satisfaction with support were identified as significant predictors of depression. The findings are consistent with previous studies that showed a higher prevalence of depressive symptoms among older individuals with lower socioeconomic status, poorer health and functional conditions, and lack of psychosocial resources (George 1996; Roberts et al. 1994; Zeiss et al. 1996). In the current study, psychosocial resources explained a considerable amount of the variance of depression even after adjusting for the effects of disease and disability.
In addition to these direct effects, mastery and satisfaction with support were shown to have significant interactions with disability in predicting depression. The association between disability and depression was stronger among individuals with lower levels of mastery and less satisfaction with support. Conversely, individuals who had greater levels of mastery and more satisfaction with support were less likely to experience depressive symptoms in the presence of disability. This finding suggests that psychosocial resources may serve as a stress moderator that buffers the adverse consequences of disability.
Mastery as an Indicator of Psychological Resilience
The present study provided further support to the considerable body of literature that showed the protective role of mastery in buffering life stress (Kempen et al. 1999; Roberts et al. 1994). The beneficial effects of mastery may be explained in several ways. First, mastery may enable individuals to prevent or effectively manage health-related problems. Studies have shown that individuals with high mastery or control are more likely to use preventive care, have good health behaviors (e.g., not smoking, exercise, and proper nutrition), seek treatment early, and use health services properly (Menec and Chipperfield 1997; Seeman and Seeman 1983). Second, mastery may help individuals effectively mobilize personal resources and coping strategies. Individuals with high mastery are likely to have more social resources and better skills to use them in times of need. Also, they are more likely to use problem-focused coping when they are confronted with stressful situations (Thoits 1987). These preventive behaviors and effective management skills associated with mastery may alter negative consequences of disability and facilitate better adaptation.
Unlike many personality traits, the stability of mastery is subject to controversy. Some studies have suggested that mastery or control is a stable construct over time (Aneshensel, Pearlin, Mullan, Zarit, and Whitlatch 1995), whereas others have viewed it as responsive to life events or situations (Schieman and Turner 1998). If mastery is a modifiable construct, it is possible that decline in physical functioning may erode individuals' levels of mastery. Then mastery may represent a psychological resource as well as a consequence of disability. To clarify the stability or change in mastery over time and to examine the feedback loop in the process, a longitudinal study design is needed.
Beneficial Effects of Social Resources
Consistent with previous studies that showed the positive effects of social integration on emotional states (George 1996), the present study found a significant connection between social network and depression. Several explanations may be considered for the effects of social network on depression. First, individuals with better social relationships with relatives and friends may be more extroverted and less vulnerable to negative emotional states. Second, older individuals with larger social networks may be more likely to participate in health-promoting activities and social events, which may in turn enhance emotional well-being. Third, individuals who are socially active and connected with others may use their networks as coping resources to confront disability and avoid depression. Finally, the feeling of support may bolster self-worth and self-esteem and lead to positive emotional well-being.
The present study showed that satisfaction with support was a significant predictor of depression, whereas received social support was not. The finding implies the importance of the role of quality of support over that of quantity of support. Studies have shown that perception of support is more meaningful than objective amount of support in predicting emotional well-being (George 1996; Wallsten et al. 1999). It is noteworthy that satisfaction with support was not only connected with fewer depressive symptoms but also interacted with disability to mitigate the harmful effects of disability on depression. This finding suggests that individuals with disability may be protected from progression of depression when they are highly satisfied with support.
Limitations and Implications
Some limitations of the present study should be noted. One important concern is the nature of the participants who were examined. The present study used a nonrepresentative sample with a low response rate. In addition, the sample was biased toward older adults of higher socioeconomic status and generally good health; therefore, extreme cases of illness and frailty are underrepresented. A second limitation is related to the nature of cross-sectional study design, which restricts the ability to draw causal inferences concerning the directionality among the constructs. The possible reciprocal relations between disability and depression and changes in each construct over time need to be explored with a longitudinal study design. The utilization of self-report as an assessment tool for disability should be noted as a limitation as well. Because self-reports are subject to individuals' emotional states or characteristics, it is possible that the association between disability and depression may be overstated by some degree. Another limitation is that we used a crude measure of chronic conditions by summing the total number of conditions without considering the severity or the unique characteristics of each condition.
In spite of the aforementioned limitations, the present study has implications for research and practice. In addition to the growing literature that suggests the importance of psychosocial resources in the disablement process (Femia et al. 1997, Femia et al. 2001; Jang et al. 2001; Kempen et al. 1999), the present study shows that they also influence how individuals promote well-being under the conditions of disability. Given that some aspects of psychosocial resources are modifiable, the present study suggests ways to enhance well-being of functionally challenged older populations. First, enhancement of sense of control and modification of environments to assist those with disability may empower functionally challenged older individuals and help them manage the adversity of disability. Research has reported that older individuals benefit from control-enhancing interventions and experience an increased sense of mastery (Reich and Zautra 1989). Second, efforts to enrich older individuals' social networks and to maximize satisfaction with support will be useful in protecting older individuals from depression. Given the finding that subjectively perceived quality of support is more meaningful than quantity of support, interventions should target both support providers to better understand elders' support needs and expectations and support-receiving elders to bolster positive evaluations and appreciation of situations. In addition, acknowledgment of positive outcomes from stressful experiences, such as finding meaning in life, developing better coping skills, and recognizing the value of social relationships, may be useful in preventing depression (Taylor, Kemeny, Reed, Bower, and Gruenewald 2000).
Along with the widely acknowledged importance of behavioral interventions, such as physical exercise and rehabilitation, psychological approaches altering individuals' feelings and perceptions need more attention. Studies have demonstrated the effectiveness of psychotherapy among disabled older individuals in reducing depression and improving functioning (Landreville and Gervais 1997), as well as educational interventions targeted to older individuals to teach new coping strategies (Zarit and Zarit 1998). Given the findings from the present study and the promising evidence for the effectiveness of therapeutic or educational interventions provided by other studies, psychosocial factors should be taken into account in designing programs for older adults with disability.
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Acknowledgments |
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Received for publication February 1, 2002. Accepted for publication June 6, 2002.
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